Lateral periodontal cyst : An unusual case report Cisto periodontal lateral : Relato de caso incomum

Introduction: Lateral periodontal cysts are odontogenic cysts with very unusual development. According to the literature, they account for less than 0.4% of cases of odontogenic cysts. Presentation of Case: The present report describes a 34-year-old patient referred to the Brazilian Journal of Development Braz. J. of Develop., Curitiba, v. 6, n. 11 , p.86470-86477, nov. 2020. ISSN 2525-8761 86471 maxillofacial surgery and traumatology department of Montenegro Hospital due to swelling of the face with asymptomatic evolution for approximately 1 year. Based on clinical and tomographic examinations, the diagnostic hypothesis was odontogenic cyst, and the surgical plan involved complete enucleation of the cystic lesion. Complete removal was performed, and the material removed was sent for histopathological analysis. The examination revealed an irregular cystic cavity covered by epithelial tissue with few cuboidal layers that showed clear cells in the basal layer in some areas and the formation of nodular epithelial structures that protruded into the cavity. Discussion: The histopathological characteristics described in the literature are consistent with the histopathological description of the enucleated cyst in this case, confirming the diagnosis of lateral periodontal cyst. Conclusion: The patient is currently under follow-up, and evaluations have been normal.

maxillofacial surgery and traumatology department of Montenegro Hospital due to swelling of the face with asymptomatic evolution for approximately 1 year. Based on clinical and tomographic examinations, the diagnostic hypothesis was odontogenic cyst, and the surgical plan involved complete enucleation of the cystic lesion. Complete removal was performed, and the material removed was sent for histopathological analysis. The examination revealed an irregular cystic cavity covered by epithelial tissue with few cuboidal layers that showed clear cells in the basal layer in some areas and the formation of nodular epithelial structures that protruded into the cavity. Discussion: The histopathological characteristics described in the literature are consistent with the histopathological description of the enucleated cyst in this case, confirming the diagnosis of lateral periodontal cyst. Conclusion: The patient is currently under follow-up, and evaluations have been normal.

INTRODUCTION
Lateral periodontal cysts are a rare type of developmental odontogenic cyst that typically occurs lateral to the tooth root surface. They have distinct histopathological, clinical and radiographic characteristics and are defined as nonkeratinized and noninflammatory developmental cysts [1][2][3][4] . These cysts likely originate from dental lamina remains, but their source is still under debate 1,2 . They are most frequently found in the region of the premolars in the mandible and represent approximately 0.4% of all odontogenic cysts 3 . These cysts have no predilection for sex or race, and their peak prevalence occurs in the sixth decade of life 5 .
Because of the asymptomatic characteristics of lateral periodontal cysts, lesions are often discovered during routine radiographic examination and appear as a well-defined solitary radiolucency adjacent to a tooth root. The lesion has a circular or oval shape and is surrounded by a radiopaque border 1,2 . The vitality of the pulp of the adjacent tooth is not affected by the cyst 6 . Lateral periodontal cysts have an average size of 1±0.6 cm 1 . Typical histological features include a cystic cavity coated with nonkeratinized squamous epithelium that sometimes penetrates the fibrous tissue, forming invaginated plaques 5,6 .
The treatment of choice for lateral periodontal cysts is surgical removal and subsequent histological evaluation to confirm the diagnosis 3 . Recent studies have used diode lasers for the surgical treatment and removal of the cyst, with good results 4 .
The objective of the study was to report a case of lateral periodontal cyst due to the rarity of the disease and its unusual characteristics.  The surgery occurred under general anaesthesia, and the patient received prophylactic antibiotic coverage with 1 g intravenous cephalothin immediately before the surgical procedure.

PRESENTATION OF CASE
A transoral buccal incision was made, and the buccal cortical bone was removed to gain access to the lesion. The thin cyst capsule was easily identified and removed from the adjacent bone.
Total enucleation of the lesion was performed with a surgical curette (Figure 2), after which haemostasis and surgical wound suture were performed. The cyst (Figure 3) was immersed in 10% formaldehyde and sent for histopathological analysis.   The patient remained in the hospital for 24 hours and was then discharged. After 10 days, the patient returned to the outpatient clinic for suture removal and began clinical follow-up.
After two years of postsurgical control, bone repair with reorganization of anatomical structures was observed in a new CT scan ( Figure 5). The patient will be followed up every six months for five years.

DISCUSSION
In this study, a case of lateral periodontal cyst was reported, and its clinical, tomographic and histological presentation was investigated. Because lateral periodontal cysts are asymptomatic, they are usually found in routine radiographic examinations. They are located near vital teeth in middle-aged patients; radiographically, the lesion shows well-defined radiolucency surrounded by a radiopaque halo 3 , as was observed in the present case. Although the literature indicates that these cysts have an average size of 1 cm 1,3 , in this case, the cyst was 3 x 4.5 cm, indicating that is was as an unusual type of lateral periodontal cyst.
Based on these findings, a provisional diagnosis of lateral periodontal cyst was established, and treatment was planned accordingly. After the enucleation of the cyst, it is always prudent to confirm the diagnosis through histopathological analysis, which should reveal a cyst that is surrounded by thin walls of non-keratinized stratified squamous epithelium that is usually without inflammation and is supported by connective tissue. Invagination of the squamous epithelium in the fibrous tissue can be observed 5  Surgical treatment is considered successful when the following criteria are met: reestablishment of stomatognathic system functions followed by total reduction of the disease focus, in this case of the lateral periodontal cyst; healing of bone and mucosal tissues; and nonrecurrence of the disease during follow-up 4 . Thus, it can be stated that the diagnosis, treatment plan and postoperative follow-up of the unusual case of a lateral periodontal cyst described in this report were successful.